title: Steam pops during irrigated radiofrequency ablation: feasibility of impedance monitoring for prevention.
abstract: BACKGROUND
  Steam pops are a risk of irrigated radiofrequency catheter ablation (RFA) and may cause cardiac perforation. Data to guide radiofrequency (RF) energy titration to avoid steam pops are limited.
  
  
  OBJECTIVE
  This study sought to assess the frequency and consequence of audible pops and to determine the feasibility of using the magnitude of impedance change to predict pops.
  
  
  METHODS
  We reviewed consecutive endocardial open-irrigated RFA for ventricular tachycardia (VT) with continuously recorded ablation data in 142 patients with structural heart disease. Steam pops were defined as an audible pop associated with a sudden spike in impedance. Ablation lesions before or after pops served as controls.
  
  
  RESULTS
  From a total of 4,107 ablation lesions, 62 (1.5%) steam pops occurred in 42 procedures in 38 patients. Perforation with tamponade occurred with 1 of 62 (2%) pops. Applications with pops had a greater impedance decrease (22 +/- 7 Omega vs. 18 +/- 8 Omega, P = .001) and a higher maximum power (45 +/- 5 W vs. 43 +/- 6 W, P = .011), but did not differ in maximum catheter tip temperature (40 degrees C +/- 4 degrees C vs. 40 degrees C +/- 4 degrees C, P = .180) from applications without pops. Eighty percent of pops occurred after impedance decreased by at least 18 Omega.
  
  
  CONCLUSIONS
  During VT ablation with open irrigation, audible pops are infrequent and do not usually cause perforation. Limiting RF power to achieve an impedance decrease of <18 Omega is a feasible method of reducing the likelihood of a pop when perforation risk is of concern.
authors.affiliation: The Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. jseiler@partners.org
authors.forename: Jens
authors.initials: J
authors.lastname: Seiler
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Roberts-Thomson
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Raymond
authors.forename: John
authors.initials: J
authors.lastname: Vest
authors.forename: Etienne
authors.initials: E
authors.lastname: Delacretaz
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001831:Body Temperature; D017115:Catheter Ablation / Q000009:adverse effects*; D017097:Electric Impedance; D005240:Feasibility Studies; D005260:Female; D006335:Heart Injuries / Q000209:etiology* / Q000517:prevention & control; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013227:Steam; D017180:Tachycardia, Ventricular / Q000601:surgery*; D007507:Therapeutic Irrigation / Q000295:instrumentation
chemical_list: D013227:Steam